Paul A. Clayton (paaronclayton.delete@this.gmail.com) on August 11, 2014 1:37 am wrote:
> David Kanter (dkanter.delete@this.realworldtech.com) on August 10, 2014 9:12 pm wrote:
> [snip]
> > And I'm quite willing to bet that no ARM server design in
> > the next 2-3 years will provide 80% of the performance
> > of the highest bin Xeon. If they are lucky, they might get to the low-end territory. They probably also
> > won't have as much memory capacity and generally be inferior across a number of dimensions.
>
> Is comparing highest bin Xeon even with the highest bin of a particular ARM implementation fair?
> The top bin Xeon might be more than twice as expensive (acquisition cost) as the ARM (both because
> it has better performance per watt and because it supports x86 software). While processor acquisition
> cost may not be especially significant in terms of total cost of operation, I am guessing it
> is not negligible. Comparing median bins seems (to me) more appropriate (as I mentioned before),
> especially as that allows for a less constrained fraction of sales.
>
> (While physics does not prevent Intel from producing twice as many Xeon chips as will be sold in order to shift
> the binning upward, it seems likely that, with Intel's volumes (even for Xeon), that economics would prevent
> such. If there was an unexpected excess of fab capacity—perhaps not entirely unreasonable given fab capacity
> must be planned long before sales volume is known—it may be cheaper to throw out a month of production to
> provide more of a high-value product and perhaps even an additional higher bin, especially if that also hurts
> competitors more than it hurts Intel. However that kind of wild speculation seems a bit weird.)
>
> In addition, comparing the highest performance x86 product with the highest performance ARM product might not
> be appropriate if TCO is being considered. Supposedly, minimum, typical, and peak power are significant factors
> in TCO. The difference between a 130W (TDP) x86 and a 90W ARM might be enough give the ARM better TCO.
>
> On a strategic level, viable competition has some value. If the cost of supporting a new ISA in addition
> to x86 is modest (even if only for a fraction of an organization's servers), then providing a check
> to Intel's power might have enough value to justify migration costs and dual maintenance costs (if
> the TCO was otherwise equal). While there is a tragedy of the commons issue, I suspect that some organizations
> are willing to make modest sacrifices for a common good. The weakness of AMD and the hype around ARM
> may facilitate such choices (i.e., the danger of an Intel monopoly is greater and the possibility
> of broader competition more credible [credibility can be increased by hype]).

If people want to compare ARM and x86 performance, then it seems like the highest bin is appropriate.

I agree that ARM can be commercially relevant in servers at lower performance points, but the OP was making noise about how ARM vs. x86 impacts design complexity/perf.

David